186 



display most of the elements in place, and several others exhibit the artic- 

 ulation of the pectoral fm. In the genera named, the clavicle is a wide bone 

 antero-posteriorly, and is connected with the epiotic by a strong osseous bar, 

 and probably with the apex of the parietal by another bar. The posterior 

 part of the arch between these connections is occupied by the stout scapula. 

 Its posterior face is principally occupied by three convex articular facets. 

 It sends a short laminar continuation downward behind the clavicle, and 

 turns inward above, with a massive body at right angles to its long axis. 

 This transverse portion is supported by the coracoid, which is a stout, flat 

 rod, narrower than the clavicle, and is appressed to the inner face of the 

 latter nearly to its distal end. Its posterior border is separated from the 

 clavicle by a deep groove, but the anterior margins are continuous. Above, 

 it incloses a large foramen with the exterior part of the scapula. It is not 

 now possible to state whether there is any prascoracoid (Parker; '' span gen- 

 stuck,' 1 Gegenbaur) ; but the upper part of the bone here called coracoid 

 occupies the position of the prsecoracoid in some fishes, articulating with the 

 superior instead of the infei'ior extremity of the scapula, as is usual. Except 

 in the elevated position of the scapula, the entire arrangement approaches 

 that of the Siluroids; but the inferior part of the scapular arch is not hori- 

 zontal as in those fishes, but vertically compressed. 



The articular facets of the scapula are convex : the inferior and largest is 

 oblique ; the median and smallest is situated behind the axis of the others. 

 Behind the superior two, on the transverse part of the scapula, are two round 

 fossae, in line, adapted for the reception of the condyles of two basilar bones. 



The pectoral fin is composed of osseous rays, of which the first is much 

 the largest, forming a powerful defensive weapon. As the fossils are found, 

 a number of these rays usually lie in close apposition, edge to edge; but they 

 are not coosified, and iu life probably diverged in the usual manner, extend- 

 ing the intervening membrane. Their component halves differ much in form, 

 and are easily separated; and, as they often occur in this condition, inex- 

 perienced persons may be led to regard them as entire spines. 



The femoral bones, or those supporting the ventral fins, are preserved in 

 specimens of Icldlujodectes and Portheus. They resemble those of many 

 physostomous fishes, but present a number of characteristic peculiarities. 

 Their posterior portion is massive and is expanded on the outer side to sup- 

 port the facets for the ventral rays. They are also expanded on the inner side, 

 and strongly united, in the case of Portheus, by suture. The anterior part of 

 these bones is thinner, and consists of two parts, — an inner rod, and an outer 

 lamina at the base of the rod. The rods, or styles, are directed forward, par- 



